The goal of the proposed research is to explore the extent and mechanism of the antagonistic effect of low level hyperbaric environments on ethanol intoxication. Experiments will be conducted in mice using sleep-time, rectal temperature, respiratory rate, mortality and signs of physical dependence as measures of the antagonistic interaction between ethanol and low level hyperbaric environments. These experiments will: (1) Determine the generality of the antagonism across strains and species; (2) Investigate the extent of the antagonism at different ethanol doses; (3) Outline the time-course of the antagonism; (4) Explore the mechanism of the antagonism. It is felt that these studies will provide further insights about the mechanism(s) by which ethanol affects the brain and behavior and may provide a useful ethanol antagonist.